Serena Williams is not ready to say goodbye just yet. Nor, clearly, are her fans. And she heard them, loud and clear. In her first match at what is expected to be the last U.S. Open — and last tournament — of her remarkable playing career, even if she insists that she won#39;t quite say so, Williams overcame a shaky start to overpower Danka Kovinic 6-3, 6-3 amid an atmosphere more akin to a festival than a farewell.